1. Field of the Invention
The present invention relates to a silica slurry having low viscosity even for a high silica concentration. This is achieved by using a silica powder having an uniform particle size and low agglomeration. The silica powder can be dispersed over a wide concentration range without precipitating and while maintaining a low viscosity. The resulting slurry is excellent in handling, stable with the passage of time, and suitable for high-speed polishing or rough polishing. Moreover, since the impurity concentration is low, it is suitable for chemical mechanical polishing of semiconductor materials. Since the silica dispersion slurry can be handled with a high concentration of silica, the supplying cost of the slurry is low.
The present invention also relates to a polishing composite which includes the above silica slurry and which has excellent performance.
2. Discussion of the Background
A dispersion slurry of fumed silica or colloidal silica has been used in a chemical mechanical polishing (CMP), (Japanese Patent Laid Open No. JP62-30333A, JP5-154760A, JP2001-342455A). Generally, a polishing process of a silicon wafer is classified into three processes, i.e., a primary polishing, a secondary polishing and a finishing polishing. It is required that after the finishing polishing the final surface has no scratch and haze. Furthermore, a high purity of the polishing slurry is strongly required in order to prevent metal ionic contaminations resulting from taking metal ions, especially sodium, into the surface layer of the substrate at the time of polishing.